My lab is interested in the genetic control of carbon partitioning in maize. To characterize genes functioning in this process we have identified mutants that hyperaccumulate starch and soluble sugars in their leaves. Initially, we have focused our attention on mutants that produce variegated leaves as we hypothesize that these may be defective in sensing or signaling the build up of carbohydrates in the tissue. The best characterized is tie-dyed1 (tdy1) which develops leaf regions containing approximately ten-fold higher levels of carbohydrates compared to wild type. Cloning the gene determined that it encodes a novel protein expressed in the phloem. From our phenotypic and molecular expression studies, we propose that TDY1 acts as a sugar flux or an osmotic stress sensor to up-regulate sugar export into the veins, possibly through controlling sucrose transporters. Intriguingly, in response to the elevated sugar levels, the ultrastructure of the cell wall is altered, which we determined is associated with increased cellulose deposition. Ongoing research focuses on determining the function of TDY1, determining the biological functions of all maize sucrose transporters, characterizing additional carbon hyperaccumulation mutants and investigating the utility of manipulating the flux of carbon to the cell wall for biofuels production.

• 'Psychedelic' maize may help increase crop and biofuel yields (Jun 2010)

• NIH Postdoctoral Fellowship, UC-Berkeley (1997-2000)
• DOE/NSF/USDA Maize Biology Training Grant Predoctoral Fellowship, University of Missouri (1996-1997)
• USDA National Needs Predoctoral Fellowship, University of Missouri (1992-1995)

Slewinski TL, Garg A, Johal GS and Braun DM. Maize SUT1 functions in phloem loading. Plant Signaling and Behavior 2010;5(6):1-4.

Slewinski TL and Braun DM. Current perspectives on the regulation of whole-plant carbohydrate partitioning. Plant Science 2010;178(4):341-349.

Slewinski TL and Braun DM. The Psychedelic genes of maize redundantly promote carbohydrate export from leaves. Genetics 2010;185(1):221-232.

Huang M and Braun DM. Genetic analyses of cell death in maize (Zea mays, Poaceae) leaves reveal a distinct pathway operating in the Camouflage1 mutant. American Journal of Botany 2010;97(2):357-364.

Slewinski TL, Meeley R and Braun DM. Sucrose transporter1 functions in phloem loading in maize leaves. Journal of Experimental Botany 2009;60(3):881-892.

Ma Y, Slewinski TL, Baker RF and Braun DM. Tie-dyed1 encodes a novel, phloem-expressed transmembrane protein that functions in carbohydrate partitioning. Plant Physiology 2009;149(1):181-194.

Huang M, Slewinski TL, Baker RF, Janick-Buckner D, Buckner B, Johal GS and Braun DM. Camouflage patterning in maize leaves results from a defect in porphobilinogen deaminase. Molecular Plant 2009;2(4):773-789.

Braun DM and Slewinski TL. Genetic control of carbon partitioning in grasses: Roles of Sucrose transporters and Tie-dyed loci in phloem loading. Plant Physiology 2009;149(1):71-81.

Slewinski TL, Ma Y, Baker RF, Huang M, Meeley R and Braun DM. Determining the role of Tie-dyed1 in starch metabolism: Epistasis analysis with a maize ADP-glucose pyrophosphorylase mutant lacking leaf starch. Journal of Heredity 2008;99(6):661-666.

Ma Y, Baker RF, Magallanes-Lundback M, Dellapenna D and Braun DM. Tie-dyed1 and Sucrose export defective1 act independently to promote carbohydrate export from maize leaves. Planta 2008;227(3):527-538.

Baker RF and Braun DM. Tie-dyed2 functions with tie-dyed1 to promote carbohydrate export from maize leaves. Plant Physiology 2008;146(3):1085-1097.

Baker RF and Braun DM. tie-dyed1 functions non-cell autonomously to control carbohydrate accumulation in maize leaves. Plant Physiology 2007;144(2):867-878.

Golubovskaya IN, Hamant O, Timofejeva L, Wang CJR, Braun D, Meeley R and Cande WZ. Alleles of afd1 dissect REC8 functions during meiotic prophase I. Journal of Cell Science 2006;119(16):3306-3315.

Braun DM, Ma Y, Inada N, Muszynski MG and Baker RF. tie-dyed1 regulates carbohydrate accumulation in maize leaves. Plant Physiology 2006;142(4):1511-1522.